Study on high‐temperature and high‐pressure measurement by using metal‐coated FBG

Metal‐coated fiber Bragg grating (MFBG) sensor was proposed to measure high‐temperature and high‐pressure condition. Metal‐coated layer of FBG improved bonding performance between metal material substrate and sensor protected as well as prolonged the lifespan of the FBG sensor. By optimized and designed thin‐wall copper cylinder structure and soldered MFBG on this, we had measured high‐temperature and high‐pressure environments. This sensor can measure the pressure range from 0 to 40 MPa. Its correlative coefficient reached 99.95% and its sensitivity was 0.0493 nm/MPa, which was about 19 times than normal Fiber Bragg Grating. Using a thermostat, a good linearity of temperature characteristic of this structure was obtained and its correlative coefficient reached 99.904%. Temperature had been measured range from 50 to 240°C. Considering FBG intrinsic advantage, it has been applied in harsh environments such as oil‐well.